Abstract: A ¹³C NMR study of a series of low molecular weight polyesters derived from ethylene glycol, diethylene glycol, 1, 4-butanediol.adipic acid and phthalic acid is reported.¹³C resonances in the five samples were assigned by model compound study, empirical rules and experimental methods. The spin-lattice relaxation time (T₁) range and nuclear overhauser enhancement(NOE) factor were measured with PRFT and inverse gated decoupling technology. Based on this information, the optimal quantitative measurement conditions were selected and the number-average molecular weight for each sample was obtained. The results are in agreement with those from terminal group analysis. It was shown that ¹³C NMR is not only suitable for structure determination, but also suitable for quantitative measurement under certain condition.

Key words: ¹³C NMR, Molecular weight measurement, Pclycsier, NOE, PRFT